[NETFILTER]: xt_helper: Do not bypass RCU

Use the @helper variable that was just obtained.

Signed-off-by: Jan Engelhardt <[e-mail]>
Signed-off-by: Patrick McHardy <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/netfilter/xt_helper.c

···
 	if (info->name[0] == '\0')
 		ret = !ret;
 	else
-		ret ^= !strncmp(master_help->helper->name, info->name,
-				strlen(master_help->helper->name));
+		ret ^= !strncmp(helper->name, info->name,
+				strlen(helper->name));
 	return ret;
 }